Componentry manufactured by SelfLube is used principally to guide or control some form of linear motion, often under considerable load. The range of possible applications is very broad: dies, molds, fixtures, special machines and heavy equipment of all types. Our components have an extremely long life -- often exceeding that of the tool or machine in which they are installed. Virtually all of our sales are for new construction.
Many of our components are Self-Lubricating. Self-lubricating components are initially more expensive than conventional components but have the advantage of having permanent lubrication built in. No additional lubrication will be required, ever. In terms of total life cycle cost (i.e., when the cost of performing periodic greasing is considered) Self-lubricating components are always less expensive than conventional components – often considerably so since with conventional components there is always the risk of the lubrication not being performed leading to premature wear out or failure.
Graphite plugs provide the self-lubrication. Graphite has some unusual properties, which make it an excellent lubricant. Chemically, it is one of three common "allotropic" forms of elemental carbon (amorphous carbon and diamond being the other two). But, in contrast to diamond, which has a very dense and very strong three-dimensional crystal structure, graphite has two-dimensional crystal structure -- strong in two dimensions but weak in the third. Its atoms are arrayed in parallel sheets that are easily sheered off, giving graphite its characteristic slippery feeling. Rub a pencil lead and it feels oily. It's not. What you feel is a peeling off of crystal sheets.
In the self-lubrication process, it is precisely these sheered off crystal sheets that provide the lubrication, somewhat like a piece of tissue paper between two pieces of glass. Initially there is no lubrication but as the two mating surfaces (i.e., bushing and shaft) move in relation to each other, a minute amount of graphite becomes distributed over the wear surface and acts as a solid lubricant. It will stay there a long time, graphite being very stable. There are some temperature limits. Although graphite sublimes at 10,000 F in a reducing atmosphere, it will oxidize in air at about 500 F so the temperature should be kept well below this. Also graphite is one of the few known substances that has a near zero coefficient of thermal expansion. When a graphite plug is embedded into a metal part, the metal part will expand with heat; the graphite plug won’t. The plug ends up loosening which restricts the temperature range to about 200 F if the plugs have any open surfaces (i.e., not constrained by a mating part).
Additional Lubrication for Components with Graphite
In general we don’t recommend it. The only exception is that when new parts are fitted together, it takes a number of cycles to distribute the graphite over the wear surface so at the onset the parts are running dry. Some customers find that it is useful to wipe a little light oil (never grease) on the wear surface which would then act as a temporary lubricant until the self-lubricating action gets started. Beyond that, any additional lubrication is actually harmful. The reason is that liquid lubricants tend to attract dirt and grit, which tends to cause premature wear of the graphite. Grease is a particular problem. Graphited components should never be greased.
Many of our components are made of aluminum bronze, which is one of the best bearing materials available. It has a combination of characteristics that is pretty tough to beat: toughness, high tensile strength and a low coefficient of friction when mated with a moving element made of hardened steel.
It also exhibits a property called formability. In the case of a slight misalignment, in a bushing, for example, the aluminum bronze has the tendency to slightly re-form or re-distribute itself along the axis of movement thus correcting (or partially correcting) the misalignment. Friction, galling and seizing are all significantly reduced. A steel bushing, in contrast, does not have this property. Any misalignment here is permanent. So an ostensibly harder and stronger steel bushing ends up not wearing nearly as well as one made of aluminum bronze. And, when it comes time to replace a worn out bushing, the steel bushing is far more likely to have damaged the pin so two components would need to be replaced. All and all aluminum bronze is a far better choice than steel. And, when it is graphite impregnated, aluminum bronze becomes a near perfect bearing material.
Originally developed by the AMPCO Company and often called AMPCO Bronze, aluminum bronze refers to a family of copper alloys (principally ASTM C954 and C959) that have a chemical composition of about 85% copper 10% aluminum and 4% iron.
Mechanical characteristics are:
C954 C959 1018 (ref)
Tensile strength (typical): 90,000 psi 110,000 psi 64,000 psi
Yield strength (typical): 32,000 psi 60,000 psi 54,000 psi
BHN Hardness: 179 286 126
Load Ratings for Aluminum Bronze Bushings
Individual applications differ but standard handbook PV values for aluminum bronze bushings (either graphited or conventional) are as follows:
Max PV = 40,000
Max P = 4,500 psi
Max V = 225 fpm
Note: Pressure (P) is force divided by bearing area. For bushings the projected area is used. The velocity (V) is in surface feet per minute. For the typical application (i.e., hardened steel mated with aluminum bronze running with lubrication) the approximate value for the static coefficient is as follows:
CFs = 0.10 to 0.16
Note: graphite components tend to be on the low side of this range; conventionally lubricated tend to be on the high side. For flat components the bearing area would typically be the area of the smaller component. For a short slide running on a long wear strip one would use the area of the slide area not the wear strip.
SelfLube engaged Detroit Testing Laboratory to perform independent testing of its products in a tough metal stamping application. Their report concluded that using precision laboratory measuring equipment, no wear could be detected after 250,000 cycles of operation.
Clean Environments - for applications, which require clean operation, SelfLube's Self-Lubricating Componentry represents an excellent choice. They completely eliminate liquid lubricants in the form of grease or oil thus significantly reducing the chance of product contamination. In addition, there is no need for an operator or maintenance person to perform periodic lubrication activities, which eliminates another potential source of contamination.
Dirty Environments - interestingly SelfLube's Self-Lubricating Componentry also works well in very dirty environments. With no liquid lubricants, there is far less opportunity to attract contaminants to bearing surfaces. In addition, there is no need for an operator or maintenance person to perform lubrication activities in dirty or potentially hazardous areas.
Long Life - SelfLube Componentry has an extremely long life, generally longer than the equipment or tooling in which it is installed.
Design Simplicity - by eliminating the need to provide for a separate lube system, fewer components are required making designs simpler and less costly.
Maintainability - by eliminating the need to perform periodic lubrication (as well as the considerable risk of not performing it at all), end user operating and maintenance cost is lowered.
Clean - by eliminating the need for liquid lubricants, SelfLube Componentry significantly reduces the risk of both product contamination and of attracting contaminants to bearing surfaces.
Cost - SelfLube Componentry helps reduce non value-added cost for both builders and end users.
Terms & Conditions
Standard credit terms of NET 30 will be established for customers whose credit/account is in good standing. For customers without established credit or unfavorable credit history, payment can be made COD or via VISA or MASTERCARD, certified check or wire transfer.
Credit limits and payment terms may be reviewed and adjusted periodically based on actual payment history and purchasing requirements. Accounts over 90 days will be suspended from shipping product until the account can be brought back within terms.
A 1.5% per month finance charge may be applied to unpaid balances over 30 days. Any reasonable cost incurred to collect past due accounts will be assessed to the customer. This includes legal expenses, collection fees and NSF charges.
All items are billed at prices in effect at the time of shipment and is FOB our plant. Prices are subject to change without notice.
Shipments are generally made via UPS or common carrier. SelfLube cannot be responsible for damage or delays encountered during such transportation.
Claims for any shortages, errors, or defects must be made within ten (10) business days from receipt of shipment.
Regularly stocked items that are unmarked and in good condition can be returned within 60 days of shipment with no restocking charge.
Items not regularly stocked that are unmarked and in good condition can be returned within 60 days of shipment but only if there is a reasonable prospect for re-selling the items based upon a review of the item's sales history. These are subject to a restocking charge.
Custom, cut to size and altered parts are not returnable.
Shipping cost is the responsibility of the customer, unless otherwise agreed upon. Returns must be pre-approved by SelfLube and an RMA issued before they will be accepted. All items are subject to inspection before replacement or issuance of a credit.
SelfLube warrants that its products conform to published specifications. No other warranty is expressed or implied. Any liability arising from items which SelfLube sells or manufactures is limited solely to the repair or replacement of the defective item or, at SelfLube's option, a refund of the purchase price. In no event shall SelfLube be liable for any incidental, consequential, or special damages of any kind or nature whatsoever.
SelfLube is a continuous improvement company and as such it makes changes and improvements to its products from time to time. SelfLube reserves the right to make such changes or even cease producing an item without notification. Diagrams and drawings in the SelfLube catalog and/or website are meant to be for reference only. Every effort is made to insure accuracy but it is not guaranteed. Current information on SelfLube's website supersedes that appearing earlier or in earlier versions of its catalog.